A transition between two pictures. The second melts in through soft, cloudy patches that sweep across the frame behind a glowing pink edge, and right at the edge the picture breaks up into small hearts that switch over a moment early or late, so the change sparkles with heart shapes.

Use it for slideshows, galleries, carousels, wedding and Valentine's pages, and page changes; because its inputs are textures, it can cross between photos, videos or two 3D scenes. Run it from 0 to 1 with one uniform, or let it play there and back on its own. Set the edge colour, width and glow, how much the edge breaks into hearts, the heart size and the patch size. The demo has three presets: Pink glow, Gold glow and Soft, and buttons to try it on your own two pictures.

What you get: a GLSL ES 3.00 fragment shader for plain WebGL2, an ES module that returns a three.js ShaderMaterial (pass your two textures as options), a Shadertoy version that reads iChannel0 and iChannel1, and a demo page that runs offline with two built-in pictures. There is also a 10-second 1920 x 1080 H.264 loop of the built-in pictures crossing there and back.

It runs in one pass, at about 1.2 ms of GPU time per frame at 1920 x 1080 on a recent laptop. The README covers wiring up your own pictures in each version, every uniform with its default and range, and performance notes.